StateMachineEXT.cs

using Monocle;
using System;
using System.Collections;
using System.Reflection;

namespace Celeste.Mod.IsaGrabBag
{
    internal static class StateMachineExt
    {
        /// <summary>
        /// Adds a state to a StateMachine.  Ripped straight from JaThePlayer lol
        /// </summary>
        /// <returns>The index of the new state</returns>
        public static int AddState(this StateMachine machine, Func<int> onUpdate, Func<IEnumerator> coroutine = null, Action begin = null, Action end = null)
        {
            Action[] begins = (Action[])StateMachine_begins.GetValue(machine);
            Func<int>[] updates = (Func<int>[])StateMachine_updates.GetValue(machine);
            Action[] ends = (Action[])StateMachine_ends.GetValue(machine);
            Func<IEnumerator>[] coroutines = (Func<IEnumerator>[])StateMachine_coroutines.GetValue(machine);
            int nextIndex = begins.Length;
            // Now let's expand the arrays
            Array.Resize(ref begins, begins.Length + 1);
            Array.Resize(ref updates, begins.Length + 1);
            Array.Resize(ref ends, begins.Length + 1);
            Array.Resize(ref coroutines, coroutines.Length + 1);
            // Store the resized arrays back into the machine
            StateMachine_begins.SetValue(machine, begins);
            StateMachine_updates.SetValue(machine, updates);
            StateMachine_ends.SetValue(machine, ends);
            StateMachine_coroutines.SetValue(machine, coroutines);
            // And now we add the new functions
            machine.SetCallbacks(nextIndex, onUpdate, coroutine, begin, end);
            return nextIndex;
        }
        private static FieldInfo StateMachine_begins = typeof(StateMachine).GetField("begins", BindingFlags.Instance | BindingFlags.NonPublic);
        private static FieldInfo StateMachine_updates = typeof(StateMachine).GetField("updates", BindingFlags.Instance | BindingFlags.NonPublic);
        private static FieldInfo StateMachine_ends = typeof(StateMachine).GetField("ends", BindingFlags.Instance | BindingFlags.NonPublic);
        private static FieldInfo StateMachine_coroutines = typeof(StateMachine).GetField("coroutines", BindingFlags.Instance | BindingFlags.NonPublic);
    }
}